function Map(el){
    //保存地图对象
    this.el=el
    //记录地图相关属性
    this.width=800
    this.height=400


}
Map.prototype.create=function(){
    //设置div宽高之类
    this.el.style.width=this.width+'px'
    this.el.style.height=this.height+'px'
    this.el.style.background='url(./bg.png)'
    this.el.style.border='10px solid green'
    this.el.style.position='relative'
}